


Lovelashed

by Askellie (NadaNine)



Category: Undertale (Video Game)
Genre: BDSM, Bondage, Dom/sub, Ecto-Penis (Undertale), Fellcest - Freeform, Fontcest, Kink Negotiation, M/M, Masochism, Rough Sex, Self-Discovery, Sibling Incest
Language: English
Status: Completed
Published: 2017-06-20
Updated: 2017-06-20
Packaged: 2018-11-16 09:59:16
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,014
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11250801
Author URL: https://archiveofourown.org/users/NadaNine/pseuds/Askellie
Summary: Sans has always enjoyed the rough handling he gets from his brother, though it's difficult to convince Papyrus not to play nice when Sans only has 1HP.





	Lovelashed

Being in Papyrus’s room has taken on a completely new set of connotations. Previously, it was practically out of bounds and any time Sans had a reason to be there he felt distinctly uncomfortable, already half-cringing and braced for the inevitable moment Papyrus turned on him and kicked him out. Now the sight of it still makes his soul pulse, its natural beat quickening, his magic feeling charged and ready, but it’s not fear he’s feeling. It’s anticipation.   
  
“Sans,” Papyrus says like he’s trying to growl, but the harsh chords of his voice stumble and break over the syllables with a sense of urgency. He backs Sans up against the door, scrabbling frantically at the lock even though Sans has no idea whom he thinks he’s keeping out. There’s no one in the house but them.  
  
“Hey bro,” Sans grins nonchalantly, as if he’s not practically pinned in place by his brother’s more intimidating frame. He leers, but otherwise feigns obliviousness to the very obvious intent in Papyrus’s actions. “You need something?”  
  
This time Papyrus _does_ growl, and Sans feels the thrill rushing through his bones. He could almost laugh at the idea that he used to be scared of his brother, the way he tiptoed around him trying not to make him angry…but now that he’s seen the other side of his brother’s fearsome mask, he knows how much of Papyrus’s temper was exaggerated flustering. When they’re together, Papyrus is nothing short of completely controlled, exquisitely careful, constantly watchful over Sans’s reactions, and while that’s almost unbearably sweet of him, Sans has to admit, he wants to see what might happen if he pushes Papyrus a little.   
  
He doesn’t actually know how Papyrus might react, and the idea is strangely exciting.  
  
Papyrus’s fists slam hard on either side of Sans’s skull, rattling the door behind him, and Sans’s pupils blow wide with a completely unfathomable interest. He should be afraid – rattled, heh, just like the door – but instead he feels his soul soar with reckless abandon he’s never felt before.   
  
“Strip!” Papyrus snaps out the command, and Sans jolts at the order, feeling his grin twitch as his own libido becomes more difficult to ignore. It’s going to be a struggle, pretending he’s not just as affected as his brother.  
  
“Hmm, like this?” he asks, jacket sliding down his shoulders by slow increments…too slowly for Papyrus’s liking, if this angry glare in his brother’s eyelights is anything to tell by. He and his brother have barely seen each other all week, conflicting schedules and Undyne’s training and extra shifts conspiring against them. Despite his brother’s indomitable willpower and his own private resolve to keep things cool and not turn into a co-dependent mess, he knows the separation has been hard on both of them even though the change to their relationship is still relatively new.   
  
He can actually see Papyrus quivering with the effort it’s taking him to hold back as Sans’s jacket finally drops to the floor with a quiet whoosh. He absently thumbs the bottom of his t-shirt, teasingly halting before pulling it up any further than his floating ribs. He’s almost trembling himself. This is suicide. Normally he makes a point of not actively flirting with danger, being a 1HP monster and all, but he trusts Papyrus absolutely and maybe he’s a little tired of the way his brother is always so gentle with him, like Sans isn’t strong enough to take him in his entirety.   
  
Papyrus is always so resolutely in control. Sans just wants to see what it’s like if he loses it a little.  
  
And it seems like he may just have found the right button to press, because with a visible crack in his composure, Papyrus snarls and lunges for Sans’s throat. For a wild moment he wonders if his little brother is going to strangle him, but instead he grabs Sans’s shirt by the collar and brutally tears it down the middle. His claws brush tantalisingly close to Sans’s ribs, but aside from the sleek slide of his leather gloves, nothing connects. Sans’s minor disappointment is secondary to the way his breath catches from being left suddenly bare above the waist. He knows his pupils are pulsing in time with his soul, broadcasting his arousal.   
  
“You insolent whelp,” Papyrus fumes, but Sans can see the blatant bulge at his brother’s crotch, and the edge in his voice is the same violent joy as when he spars with Undyne. “Do you think you can toy with me!?”  
  
“Dunno, bro. I thought you still liked toys,” Sans taunts back, casting a pointed look over at his brother’s ‘strategy simulator’ which was really only a table set up with action figures supposedly representing different monsters in the underground. They’re the same figures his brother had enjoyed as a babybones, and though Sans has never actually caught him at it, he suspects Papyrus occasionally still uses them in much the same way.   
  
It’s a terrible idea, of course, to insinuate anything that might tarnish his brother’s pride. With a wordless bellow of outrage Sans finds himself lifted by his brother’s effortless strength and slammed back into the wall, the impact jolting all the way through his body, leaving him dizzy and making his toes curl in sudden yearning.   
  
_Fuck!_ It aches, but deliciously so, making him squirm in his brother’s hold not from the discomfort of the pain but from the even more insistent attention being demanded by his own erection. It’s taken shape between his legs suddenly and entirely without permission, the conjured flesh already throbbing with the need for touch. Papyrus shifts his hold to pin Sans with one hand and tears his shorts down with such force that Sans yelps from the snap of elastic breaking against his bones. His hips buck desperately at the empty air, but there’s still enough space between Papyrus’s body and his own that nothing connects. He whines in frustration.  
  
Papyrus seems mollified by his wantonness. “Look at you. So you were only pretending after all. You’re already dripping, brother.”  
  
He is, with unexpected fervor and intensity, the nearly translucent liquid beading over his slit before tricking down the length of his shaft. He doesn’t want Papyrus to let go of his harsh hold, but he struggles anyway, delighting in the way his bones bend and contort and feeling the way they burn with unfamiliar but wholly welcome pain.   
  
He enjoys this, he realises with sudden clarity. He likes that warning tingle of hurt that only enhances his pleasure. He’s never even imagined that pain could feel good, has always avoided it prudently, wary of anything that could cause his fragile hold on his life-force to slip, but though Papyrus can clearly hurt him, he still feels completely safe. Even through the barrier of his armour, he can seen Papyrus’s soul searing with furious desire…a desire for _him,_ for Sans, for his weakling runt brother, but right now it’s impossible to lose himself in his usual cynical self-reflections with Papyrus glaring at him with insatiable hunger.   
  
He moans, not caring how lewd he sounds or how shameful he looks. He looks into his brother’s sockets, grasping weakly at his wrists. “Pap, Pap-!”  
  
Papyrus grunts, ripping his belt free so carelessly Sans thinks the buckle might have torn, but he doesn’t care at all because he can see the glow from his brother’s cock lining up beneath him and he has only a moment to try and form an entrance to complement it before Papyrus drags him downward and impales him in one swift, merciless movement.   
  
Sans shrieks, body convulsing, because even though he’s more aroused than he thinks he’s ever been, there’d been no chance for his magic to lubricate or ready itself for the intrusion. Normally he has no trouble accommodating his brother’s size, but then usually Papyrus takes great pains to ensure that he wont hurt Sans during their consummation, taking his time, exploring first with his fingers and his tongue, whispering sultry directions and affirmations against Sans’s skull. This time he’s had none of that. His passage feels too tight and inflexible, straining to contain his brother’s cock, but that only makes Sans gloriously aware of how it feels inside him, stretching him out, making him feel so full and  thoroughly claimed. It’s unbearably erotic, and he stutters out a moan, clinging tightly to his brother as he dazedly coming down from that initial, brilliant high.  
  
Only he starts to become aware that after the initial thrust, his brother hasn’t been moving. He’s locked in place as if frozen, his body suddenly full of a tension that wasn’t there before. Sans can’t face him properly with his skull pressed into his brother’s neckbones, but he tightens his hold to try and jar his brother from stillness. “B-bro?”  
  
“I’m sorry, Sans,” Papyrus says, his voice unexpectedly tight with an emotion Sans can hardly identify. He thinks it might be remorse. “I was…I wasn’t thinking. Are you all right? Did I-?”  
  
“Pap,” he says as sternly as he can manage, which admittedly isn’t very. He’s too breathless, too taut around his brother’s cock, and now, absurdly, he has to keep himself from breaking out into highly inappropriate laughter. He doesn’t think Papyrus would forgive him. “Pap. I’m fine. You didn’t hurt me.”  
  
Papyrus reels back, and the movement somehow manages to shove his cock even deeper into Sans’s pelvis. He groans helplessly, eyelights rolling, which only seems to distress Papyrus more. “But you’re-!”  
  
Sans interrupts him with a wheeze, shaking his head. It’s so damn hard to think straight like this, but he supposes that was a poor choice of words given the way he cried out. “I mean…I like it, bro. It’s so good. It’s so fucking good, don’t you dare stop-!”  
  
Papyrus shifts again, perhaps unintentionally, and Sans makes a trill of noise that much more succinctly conveys his pleasure. He gasps wetly, feeling his sockets pricking with tears, but even that sensation feels oddly pleasant; cathartic. The pain makes him feel helpless but also oddly safe, especially with Papyrus’s arms around him.  
  
“M-more, please!” he whines, nuzzling insistently at his brother’s throat. The lack of movement is starting to burn in a different way, and he can feel his magic clenching anxiously around his brother, constricting the already tight space. He knows his brother likes to hear him beg, but usually it has to be ordered out him. He’s never done it so willingly and entirely of his own volition. “Please, Pap, please, I need you! Fuck me hard, just like thiiiiiii-ah!”  
  
Apparently that’s enough to convince Papyrus to oblige him, because he feels himself being shoved back into the wall (with slightly less force, this time) and suddenly Papyrus is fucking him with a desperation that Sans wouldn’t have imagined him capable of. Papyrus must have really struggled to hold back in order to ascertain that Sans was okay, because it feels like he’s lost all sense of restraint. Sans can do nothing but grip him fiercely and wail with every powerful thrust, his body jerking against the pull of gravity as Papyrus seems intent on somehow finding ways to plunge into him even more thoroughly.  
  
His magic burns warningly from the abuse, crackling threateningly with the possibility of tearing apart entirely, but that just adds an element of electrical friction to his brother’s thrusting. His soul is sparking urgently, the pleasure quickly becoming overwhelming, but he strains to hold out because he wants to experience every minute of this. He wants his brother’s possessive fury to be scorched into his bones, into his essence, to leave a mark on him that’ll linger like bruises, like scars.   
  
He’s going to feel this for _days_ , and the idea is so carnally appealing he feels his body instinctively tighten with the impending rush of orgasm until he’s hollering incoherently in utter ecstasy.  
  
Most orgasms leave him with a sort of loose exhaustion, but this one has filled him with a tingling energy that vibrates through his bones. He claws eagerly at his brother, licking up the side of his jaw, gasping with further want until Papyrus lets out a guttural sound and yanks him away from the wall and unceremoniously throws him down onto the bed.   
  
“I’m not finished with you,” he declares, roughly manhandling Sans into a more fuckable position. Sans tries to find his own balance only to have Papyrus snatch his wrists and pin them tightly at his back, pressed so hard against his spine it stings. His face is pressed hard into the sheets, his hips lifted by a stringent grip on his spine that forces his pelvis to lift. The pose is unabashedly crude, and Sans almost lets out a grumbling protest before Papyrus leans over him and ploughs into him once more.  
  
The angle is merciless, his brother’s cock entering him in a way that forces his spine to contort and his magic flex unnaturally to accommodate him. The added weight of his brother atop him forces him harshly into the mattress. He can barely move, can hardly think, but each clash of their bones against each other, frenzied and careless, makes him moan with unrestrained enjoyment. He doesn’t think his body can reach its peak again so quickly after the first time, but he doesn’t need the climax. It feels so good, throbbing and sore and used; a helpless receptacle for Papyrus’s pleasure.  
  
A particularly ragged thrust makes him sob, his brother’s pubis thudding against his delicate coccyx like a punishing slap, his magic distending downward into the area his stomach would occupy if he had such organs. There’s tears pouring unrestrained from his eyesockets now, his face burning from overstimulation and desperate pleasure. For a terrible moment he fears his brother is going to halt and check on him again –  he doesn’t think he can string together a coherent reassurance this time – but instead there’s a rattling tremor that he’s come to recognise as as the signal of his brother’s impending climax. The grip on his spine tightens until the bone creaks, sharp nails scratching at the vertebrae, and suddenly he’s filled with a rush of hot, salty liquid as Papyrus shudders through his peak with a soft but surprisingly sweet groan of relief.  
  
There’s a moment of stillness as Papyrus collects himself. Sans basks in it, full of contentment and tender affection, as well as an odd sense of pride to have born his brother’s harsh treatment. He even lets out a whine of complaint when Papyrus finally pulls out of him, but there’s enough residual hurt from the abrasions on the inside of his passage, made even more sensitive by the seeping of raw, magical ejaculate inside him, to leave him satisfied. He’s thoroughly limp as Papyrus turns him over, taking one look at Sans’s slack, messy face before pulling him into a tight embrace that speaks volumes. Papyrus isn’t very good at initiating a more gentle sort of intimacy. Normally he complains when Sans wants to cuddle him, always complaining about how messy his brother gets after sex and despairing over getting any slimy fluids on his bones.  
  
“You’re okay?” Papyrus asks, his gruff tone somewhere between a question and a statement…as if daring Sans to be anything other than okay in the hands of the Great and Terrible Papyrus.   
  
“Mmmmm,” Sans sighs agreeably, squirming in Papyrus’s lap. His tail-bone feels delightfully tender, and he hasn’t yet dissipated his magic. He’s still enjoying the raw ache. “S'good, bro.”  
  
Papyrus tuts, fussily smoothing away some of the wet trails down Sans’s cheeks. “You’re such a degenerate, brother. Filthy, deviant, shameless-”  
  
“Did you like it?” Sans asks, suddenly aghast at the idea that maybe Papyrus hadn’t enjoyed the roughness the way Sans had. His brother had always made such a point of being meticulous, careful and controlled during sex, and maybe is simply how he prefers it. If Sans had read him wrong…  
  
Papyrus flushes unexpectedly, spluttering. “Well, I-! I may have gotten slightly carried away but you were making things very difficult! Honestly, Sans, I should gag that insolent mouth of yours-”  
  
“Maybe you should,” Sans offers insolently, feeling his smirk return. “Would you like that, Papy?”  
  
His brother stops cold, and Sans can practically see the lucid image going through his brother’s thoughts, his flush glowing a few increments brighter. Sans makes the mistake of snickering, and with an offended look Papyrus abruptly dumps him out of his lap, ending the brief moment of tenderness.  
  
“I always enjoy myself,” Papyrus informs him, an admittance that’s more honest than it needs to be. Sans blinks at him, almost surprised before remembering Papyrus’s insistence on 'researching’ the keys to successful, mutually satisfying relationships. Clear communication is an important factor, he’s told Sans time and again. “But that was…unexpectedly invigorating. As long as you are sure there will be no lasting consequences to your health, I would be open to trying it again.”  
  
There’s no hiding the rattle of excitement that goes through Sans’s bones. Papyrus pointedly rolls his eyes at him. “In which case, next time you should just tell me what it is that you want instead of goading me into it. I would prefer not to harm you by accident.” He considers for a moment, and offers Sans a crooked, fanged grin. “Only intentionally.”  
  
Sans feels a bit sheepish. He’s pretty bad at the 'clear communication’ thing. It’s much less vulnerable to just hint and and try to manipulate the right outcome to get what he wants. “Right. Sorry, Boss.”  
  
Papyrus makes a dismissive sound, waving it off. “Thankfully, you have a truly great brother who knows how to take care of you.”  
  
“You’re the best,” Sans agrees sincerely, creeping nearer to nestle against his brother’s side. Papyrus stiffens for a moment, and then wordlessly puts his arm around Sans, permitting the closeness. Moments like these are few and far between. They might as well enjoy it while it lasts.


End file.
